Liquid crystal display device has been widely disseminated as a device for displaying image. By characteristic of its controllability of light based on retardation, the liquid crystal display device employs optical compensation based on retardation, for higher image quality. A general mode of embodiment of the optical compensation is such as using an optically anisotropic layer composed of a birefringent polymer film.
JP-A-2009-086260 describes a retardation film which comprises a transparent substrate composed of a cellulose derivative and an optically anisotropic layer which is formed on the transparent substrate, contains a rod-like compound having refractive index anisotropy, and satisfies nx1>ny1≥nz1, where nx1 is refractive index in the direction x of in-plane slow axis, ny1 is refractive index in the direction y of fast axis, and nz1 is refractive index in the thickness direction z, and which has a bendability of 16 mm or smaller.
Many of the optically anisotropic layer are often configured by thermotropic liquid crystal, as a liquid crystal material for configuring it. However, the thermotropic material tends to be destabilized depending on environmental temperature. Therefore, the thermal stability is enhanced by introducing a polymerizable group into the liquid crystalline compound composing the liquid crystal material and fixing the state of alignment of the liquid crystalline compound by polymerization.